The prior art is generally cognizant of the use of tools which may be scanned or measured by instruments in order to establish a standard against which future measurements may be measured. As an example, U.S. Pat. No. 4,014,109 discloses a phantom of a human figure which includes therein material which may be imaged externally so as to test the sensitivity of the measuring device. Other patents which show the use of such passive calibrating device for calibration or testing of a wide variety of radiation instruments and devices are U.S. Pat. No. 2,280,905, U.S. Pat. No. 3,778,837, U.S. Pat. No. 3,791,192, U.S. Pat. No. 3,933,026, U.S. Pat. No. 3,986,384, U.S. Pat. No. 4,028,545, U.S. Pat. No. 4,033,880, U.S. Pat. No. 4,154,672.
The assignee of the present patent application has also previously manufactured a test tool for use in non-computerized radiographic tomography, also called ordinary tomography, which includes a cylindrical section of plastic material having embedded therein twelve lead alloy numbers arranged in a helical pattern. By imaging that tool with a radiographic tomographic apparatus, it was possible to determine the location of the plane and the general thickness of cut of such a tomographic unit by examination of the resulting image. This tool is used exclusively with non-computer aided tomographic devices.